Try the public library and see what the genealogy room has in the way of cemetery books.
More than likely, his grave would have been marked with a government issued marker and
he is in a marked grave in the VanBuren area and those cemetery books will tell you which one.
It is a long shot but his death may have made the papers, so check those.
In Little Rock, there is the History Commission which has all those old papers, on film.
Or try the nearest LDS Family Library to see what they have or can find.
This is not an impossible task, just one you have to do by the process of elimination.
Good luck.